Manhole cover



April 19, 1938.

J. R. MA CLEAR MANHOLE CQVER Original Filed May 12, 1956 INVENT OR.

misfi? Mai/4x? ATTORNEY.

Patented Apr. 19, 1938 UNITED STATES MANHOLE COVER James R. Maclear, Denver, Colo.

.ApplicationiMay 12, 1936, Serial No. 79,245

Renewed February 12, 1938 This invention relates to the type of manhole cover usually employed in streets and alleyways for allowing access to sewers, telephone lines, and other underground equipment.

The principal object of the invention is to provide a simple and eflicient mechanism for locking the manhole cover against its supporting ring, so that it will not rattle under the passage of vehicles; so that it can not be accidentally dis- 10 placed; and so that it will not be blown from place by explosions, internal pressures, etc.

Another object of the invention is to so construct the locking mechanism that it will not be affected by the rust and corrosion to which all 16 underground equipment is subjected.

A further object is to provide a locking mechanism on a manhole cover which will require no change in the usual manhole ring and which will accommodate manhole rings of various depths or m thicknesses so that it can be installed in place of the present covers, without change in the supporting rings.

Other objects and advantages reside in the detail construction of the invention, which is de- 25 signed for simplicity, economy, and efiiciency.

These will become more apparent from the following description.

In the following detailed description of the invention reference is had to the accompanying 30 drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

In the drawing:

Fig. 1 is a plan view of a manhole ring with 35 the improved cover in place therein.

Fig. 2 is a bottom view thereof looking upwardly.

Fig. 3 is an enlarged cross section taken on the line 33, Fig. 1.

40 Fig. 4 is an enlarged vertical section through the locking member.

Fig. 5 is a cross section through the locking member, taken on the line 5-5, Fig. 4.

Fig. 6 is a detail face view of the locking cam.

45 Fig. 7 illustrates an alternate arrangement of the locking cam.

A typical manhole ring of a variety most commonly used is indicated at H]. Such rings have a depth or thickness equal to the pavement in 50 which they are set. The ring is provided at its bottom with a retaining flange H and at its top with a lid groove l2.

The improved manhole cover is designed to set in any of the usual manhole rings ID. The

55 cover comprises a circular cast lid l3 provided on its bottom with suitable strengthening ribs Id. In applying the newinvention to the cover. a series of bearing bosses l5 are extended downwardly from the bottom thereof adjacent the periphery. Each of these bosses is drilled to re- 6 ceive a rotatable plug member [6 having an enlarged head I! which rests in a counterbore in the top of the plate l3. A suitable wrench socket I8 is formed in the head II. The tops of the heads I! are flush with the top of the cover I3. 10

A shaft I9 projects from the plug I6. The shaft I9 is preferably cast into the plug [6 at the time of casting the latter. It is preferred to form the shaft l9 of square cross section, whereas the plug I6 has a cylindrical cross section. A

series of clamping notches are formed in the opposite faces of the shaft [9 throughout its length. These notches are for holding a cam arm 2| in any desired vertical position along the shaft l9.

The cam arm 2| is clamped to the shaft l9 by means of a suitable clamping cap 22 and clamping bolts 23. The cam arm terminates in an inclined cam surface 24.

In fitting the improved cover to the ring Ill, 25 the lid is placed in the ring groove [2 and the cam arms 24 are brought to a position slightly higher than the bottom edge of the ring. They are then permanently clamped in this position by means of the clamp bolts 23. Both the cam arm and the clamping cap are notched to fit the notches 20 in the shaft l9 so that after they are drawn into position, they cannot move along the shaft.

To clamp the cover in place it is only necessary to rotate the heads I! so as to bring the inclined cam surfaces 24 against the bottom of the ring ID. The wedging action of these surfaces draws downwardly on the shafts l9 firmly clamping the lid [3 in place. The angle of the inclined surface 24 is such that the cam arms will not back out or rotate from the usual vibration to which the lid is subjected. They must be manually rotated by a suitable wrench to disengage them from the ring I0.

In Figs. 4 and 6,' the notches 20 are formed in opposite faces of the shaft l9. They could however be formed in opposite corners of this shaft in which case a clamping arm and cap such as shown in Fig. '7 would be employed with lugs 25 in the corners of their sockets to enter the corner notches.

While a wrench socket has. been illustrated on the drawing in the head II, this head could be formed so as to have external nut faces for reception of a socket wrench if desired.

It has been found that if a series of concentric labyrinth grooves 26 are cut beneath the head l1, they will prevent dust, dirt, and moisture from reaching the plugs l6. They also act to hold a lubricant in place therein to maintain the bearing surfaces lubricated and prevent corrosion thereof. The notches 20 also serve to lock the shafts into the metal of the cast plugs I'G.

While a specific form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within the scope of the appended claims, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent is:

1. A manhole cover plate for attachment to a supporting ring, said plate having a tubular bearing boss projecting downwardly from its under surface, the upper surface having a depressed area in its upper surface, surrounding the open ing in the boss; a shaft journalled in the bearing, the upper'end of the shaft having a head, positioned in the depressed area, and accessible for rotating the shaft, the outer surface of the shaft, below the bearing, having spaced notches, a two part cam arm for attachment to the shaft; means on the cam arm for engaging the notches on the bolt; and means for effecting a clamping engagement between the cam arm and the bolt.

2. A manhole cover plate for attachment to the topof a supporting ring, said plate having a tubular bearing boss projecting downwardly from its under surface, the upper surface of the cover having a depressed area surrounding the upper end of the opening in the bearing boss; a headed cylindrical plug journaled in the bearing with its head in the depressed area; a shaft having its upper end attached to the plug; a two part cam arm; and means for clamping the cam arm to the shaft.

JAMES R. MACLEAR. 

